Stone-throwing chimp plans his attacks

A chimpanzee at a Swedish zoo has shown an ability to plan for future events by hoarding stones to fling at visitors.

The surly chimp calmly collects stones and broken pieces of concrete while no-one’s around, and stockpiles them for later use. When zoo visitors later appear at his fence to ogle him, he unleashes his cache of weaponry in an “agitated state”.

“We’ve done experimental studies, and the chimps … show very clearly that they do plan for future needs, but … perhaps this was an experimental artefact,” Dr Mathias Osvath, a cognitive scientist from Lund University, told BBC News.

“Now we have this spontaneous behaviour, which is always in some sense better evidence.”

The chimpanzee, named Santino, seems singularly ill-disposed to zoo visitors. Keepers have removed hundreds of his missiles over the years, which are only ever used to pelt members of the public. During zoo-closure periods, Santino neither hoards nor throws his missiles.

The angry ape shows a surprising determination to batter Joe Public. Even when stones are in short supply, he taps portions of his concrete enclosure and listens for weak points, before breaking off pieces loosened by the Scandinavian frost.

During threat displays, chimpanzees are known to throw whatever comes to hand. Frequently, however, this has come straight out of their arses.

“Spontaneous and unambiguous planning behaviours for future states by non-humans have not previously been reported,” Osvath writes in an article for Current Biology.